Agglomerating finely divided agglomerative materials in a rotating drum with co-rotating scraper

ABSTRACT

The agglomerating drum has a generally cylindrical configuration with an inner cylindrical wall. A scraper is rotatably positioned within the agglomerating drum in spaced relation to the inner cylindrical wall with its axis spaced from the axis of the drum. The scraper has a tubular body portion with a plurality of parallel rows of blades extending radially therefrom. Each of the rows extends lengthwise along substantially the entire length of the scraper body portion and follow a helical path having a single turn about the axis of the tubular body portion. Agglomerative material is introduced into the rotating agglomerating drum and forms a layer of agglomerative material on the drum inner cylindrical wall. The scraper is rotated in the same direction as the direction of rotation of the agglomerating drum and at a preselected synchronous speed with the agglomerating drum. The rows of parallel blades on the scraper form a plurality of spaced elongated generally longitudinal ridges and valleys in the layer of agglomerative material on the drum cylindrical wall. The ridges have a slight arcuate configuration and form less than a single convolution throughout the entire length of the agglomerating drum. The spaced elongated ridges in the layer of agglomerative material extend lengthwise in the drum substantially parallel to the axis of the drum and serve as longitudinally extending lifters to mix and agitate other particulate agglomerative materials introduced into the drum by lifting portions of the other particulate agglomerative material from the underside of the bed and depositing the material on the upper surface of the bed.

This application is a continuation of Ser. No. 466,832, filed on May 3,1974, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a method and an apparatus for agglomeratingfinely divided agglomerative materials in a rotating drum and moreparticularly to a method and an apparatus for agglomerating finelydivided coal particles and finely divided particles of carbonaceousresidue in a rotating drum to form carbonaceous agglomerates.

2. Description of the Prior Art

The process for making formcoke as described in U.S. Pat. Nos.3,073,751; 3,401,089 and 3,562,783 includes introducing particulatebituminous coal and finely divided char (the solid carbonaceous residueof coal which has been distilled at a temperature of between 800° and1400° F.) in a rotary retort. Depending on the type of coal employed andthe ratio of coal to char, pitch may also be added as a binder and toincrease the strength of the agglomerates formed in this process.Preferably, the particulate coal and finely divided char are heated toan elevated temperature before they are introduced into the rotaryretort so that the constituents supply as sensible heat substantiallyall of the heat required to achieve the desired temperature foragglomerating the carbonaceous materials.

During the agglomeration process the retort is rotated to effectintimate mixing of the constituents and tumbling of the agglomerates asthey are formed. As the constituents are mixed in the retort the coalparticles are further heated to such extent that partial distillation ofthe coal particles occurs, evolving tar and forming a loosely coherentplastic sticky mass in the retort. Where a pitch binder is employed itfurther contributes to the agglomeration of the particulate materialwithin the retort.

It is believed that the loosely coherent plastic mass formed in therotary retort breaks up during tumbling into relatively fine plasticparticles. Growth of the plastic particles is attained by a snowballingtype of tumbling or rolling action on the upper exposed inclined surfaceof the plastic mass of particulate material in the retort. Repeatedtumbling or rolling of the particles causes the continued growth of theplastic particles into agglomerates. The agglomerates continue to growuntil the binder evolved by the coal particles and the pitch binder, ifemployed, loses its plasticity. Thereafter, the agglomerates rigidifyand the growth process is stopped. The agglomerates recovered from theagglomerating retort are thereafter calcined at an elevated temperaturebetween 1500° and 1800° F. and formcoke is obtained that has strengthand abrasion resistance that is equal or superior to that ofconventional blast furnace coke. One of the objectives of the abovedescribed formcoke process is to form closely sized agglomerates havinga suitable size range as, for example, a size range of between 3/4 × 2inches or a size range of between 1 inch × 3 inches. Oversizedagglomerates, i.e. agglomerates having a size greater than the desiredsize, and undersized agglomerates, i.e. agglomerates having a size lessthan the desired size, may not be suitable for use in a conventionalblast furnace or other conventional metallurgical processes.

It has been discovered that, in conventional sized retorts, agglomeratesof a suitable size range can be obtained in shallow beds where the ratioof the absolute bed depth of the particulate material to the diameter ofthe retort is maintained below a critical value. The absolute bed depthdesignates the true dimensional depth of the bed occupied by thecarbonaceous materials and is measured at the deepest point in the bedof carbonaceous material within the rotary retort. It has been foundwhere the ratio of absolute bed depth to retort diameter is maintainedbelow the critical ratio (shallow bed) substantially all of theagglomerates have a size less than 4 inches and a substantial portion ofthe agglomerates have a suitable size range. Where, however, the ratioof absolute bed depth to retort diameter is increased above the criticalratio to form a deep bed the agglomerate product formed has asubstantial quantity of agglomerates with a size greater than 4 inchesand a reduced quantity of agglomerates with the suitable size range.

From an economic standpoint it is desirable to use retorts having aslarge a diameter as possible and to maintain as deep a bed ofcarbonaceous material as possible in the rotating retort. With theseconditions, however, it is also essential that the size range of theagglomerate product formed be within the suitable size range.

In U.S. Pat. Nos. 3,368,012 and 3,460,195 there is disclosed a rotaryretort for agglomerating carbonaceous material in a deep bed in whichthe ratio of absolute bed depth to retort diameter may be increasedabove the aforementioned critical ratio and a substantial yield ofagglomerates of a suitable size range is obtained. In accordance withthe teaching of these patents, preheated particulate bituminous coal andfinely divided char are agglomerated into a rotary retort that has aplurality of longitudinally extending rakes secured to the rotary retortinner cylindrical wall. Each of the rakes has a plurality of tinesextending inwardly toward the center of the rotary retort and the tineshave a length between one-fourth and one-third the diameter of therotary retort. The tines on the rakes are spaced from each other apreselected distance to relieve the compaction pressure exerted on thebed of carbonaceous material and to control the size of the agglomeratesformed in the retort. An agglomerate product having a suitable sizerange is obtained even when the ratio of absolute bed depth to retortdiameter is increased substantially above the ratio previouslyconsidered the critical ratio to obtain an acceptable yield ofagglomerates having a suitable size range.

During the agglomeration process the carbonaceous materials have atendency to adhere as a sticky plastic mass to the inner wall of therotary retort and to the rake tines. Separate apparatus is required toremove the accumulation of agglomerated carbonaceous materials adheringto the retort wall and to the rake tines. Because of the tine spacingdifficulty is encountered in removing the deposits of carbonaceousmaterial on the retort wall and on the rake tines. Further, asubstantial amount of energy is required to rotate the retort while theapparatus, such as a fixed scraper device, removes the carbonaceousdeposits from the retort inner wall and rake tines.

It is also known in the agglomeration of agglomerative materials that asmooth inner cylindrical wall of the rotary drum or retort is not theoptimum surface for forming agglomerates. Various types of metalliclifters for the agglomerative material within the rotary drum have beenproposed as, for example, the lifters disclosed in U.S. Pat. Nos.3,124,338; 2,695,221; 2,926,079; 2,213,056 and 3,689,044. These liftersare not suitable, however, where the agglomerative material has atendency to adhere to the inner wall of the drum. After a short periodof time a layer of the agglomerative material is formed on the wall ofthe drum to a depth that is equal to or greater than the height of themetallic lifters. This layer of agglomerative material reduces and sooneliminates the effect of the metallic lifters.

U.S. Pat. No. 3,348,262 discloses a fixed scraper for controlling thethickness of the layer of coating of agglomerative material deposited onthe inner surface of the rotating drum. The layer has a uniformthickness and a generally relatively smooth surface. U.S. Pat. Nos.2,697,068 and 3,316,585 disclose rotary scrapers positioned within therotary drum that are arranged to continuously remove agglomerativematerial from the inner wall of the drum and maintain a layer of theagglomerative material of a preselected uniform thickness on the wall ofthe drum. It is stated the layer of agglomerative material provides asurface that is superior to a smooth cylindrical wall.

U.S. Pat. No. 2,831,210 discloses a cutter bar positioned within therotary drum adjacent the inner wall of the drum. The cutter bar hasspaced teeth extending toward the drum inner wall. The cutter bar isarranged to reciprocate longitudinally relative to the drum wall and cuta series of allochiral left and right hand helical grooves in the layerof agglomerative material deposited on the drum inner wall. The rate ofreciprocation of the cutter bar and the speed of rotation of the drumare controlled so that the helical grooves do not track each other onsuccessive strokes of the cutter bar and thus provide a controlledroughness to the surface of the layer of agglomerative material on thedrum inner wall. It is stated the roughened surface of the layer issuperior to a smooth surface.

U.S. Pat. No. 2,778,056 discloses an agglomerating drum with a scraperpositioned therein. The drum and scraper are arranged to rotate atpreselected synchronous speeds with the scraper rotating in a directionopposite to the direction of drum rotation. The scraper disclosed is inthe form of a "ribbon flight" conveyor and forms multiple convolutionsof helical grooves in material adhering to the inner surface of thedrum. The convolutions of the main portion of the scaper have thedirection of a right handed thread so that the multiple convolutionsformed in the surface of the material adhering to the inner surface ofthe drum are so inclined that loose material in the grooves tends tomove back toward the inlet of the drum. Adjacent the ends of the drumthe direction of thread rotation of the scraper is reversed to minimizespillage of the material fed into the drum and also accelerate thedischarge of the agglomerates formed. The helical grooves formed in thematerial adhering to the inner surface of the drum extend generallycircumferentially around the inner surface of the drum so that thematerial within the drum tends to roll or slide downwardly within thegrooves and be carried back towards the entrance of the drum. The ridgesformed between the grooves because of their generally circumferentialarrangement around the inner surface of the drum do not function aslifters to mix the material within the drum.

In a method and an apparatus known to applicants for agglomeratingfinely divided agglomerative material in which a limited number ofgenerally longitudinally extending ridges and valleys can be formed in alayer of agglomerative material deposited on the inner wall of a drum.The ridges and valleys are formed by an elongated scraper devicepositioned adjacent the drum inner wall and arranged to rotate in adirection opposite to the direction of the drum. The height of theridges formed by the method and apparatus disclosed in the abovementioned co-pending application are limited by the direction ofrotation of the scraper device relative to the drum. For example, wherethe scraper has a pair of radially opposed blades extendinglongitudinally along the scraper tube and where a maximum height of theridge is desired only four ridges can be formed around the periphery ofthe interior wall of the drum. As the number of ridges increase theheight of the ridges decrease. Thus, limitations on ridge height and thenumber of ridges formed in the wall are present where the rotary scraperrotates in a direction opposite to the direction of drum rotation. Undercertain agglomerative conditions it is highly desirable for optimumagglomerative conditions to have a plurality of ridges of a heightgreater than the height attainable by rotating the scraper in adirection opposite to the drum and further to provide a greater numberof ridges on the periphery of the drum having the desired ridge height.

There is a need for a method and apparatus to provide elongatedgenerally longitudinally extending ridges and valleys in a layer ofagglomerative material deposited on the drum inner wall and to furtherprovide a greater number of elongated ridges and elongated ridges havinga greater height than is possible with the method and apparatusdisclosed in the above named co-pending application so that the otheragglomerative material fed into the drum is more effectively lifted andmixed.

SUMMARY OF THE INVENTION

This invention relates to a method and an apparatus for agglomeratingfinely divided agglomerative material in a rotating drum. The methodincludes feeding finely divided agglomerative material into a drumrotating about its longitudinal axis and having a generally cylindricalinner wall. The rotation of the drum deposits a layer of the finelydivided agglomerative material on the drum inner wall and rotating ascraper in the drum in the same direction as the direction of rotationof the drum at a preselected speed relative to the drum speed to form aplurality of elongated longitudinally extending alternating ridges andvalleys in the layer of finely divided material deposited on the druminner wall. The ridges and valleys are substantially parallel to thelongitudinal axis of the drum. The method further includes maintainingthe ridges and valleys so formed in the layer deposited on the druminner wall while rotating the drum and forming agglomerates from otherfinely divided agglomerative material introduced into the rotary drum.The number of ridges is a whole number and the number of ridges isdetermined by the following formula. ##EQU1## wherein N = number ofridges formed

b = number of scraper blades

U₁ = drum speed, rpm

U₂ = scraper speed, rpm.

The apparatus for agglomerating the finely divided agglomerativematerial includes a cylindrical rotary drum having an inner wall. Meansare provided to rotate the drum about its longitudinal axis at apreselected speed and deposit a layer of the finely dividedagglomerative material on the drum inner wall. A rotary scraper withblade means extending outwardly therefrom is rotatably supported in thedrum in spaced relation to the drum inner wall with the longitudinalaxis of the rotary scraper spaced from the longitudinal axis of therotary drum. Means are provided to rotate the rotary scraper in the samedirection as the direction of rotation of the drum in timed relation tothe rotation of the drum and provide relative movement between therotary drum inner wall and the scraper blade means to form a pluralityof longitudinally extending alternating ridges and valleys in the layerof agglomerative material deposited on the drum inner wall. The rotaryscraper is further arranged to remove other finely divided agglomerativematerial deposited on the surface of the ridges and valleys that havebeen formed in the layer of finely divided agglomerative material.

The above method and apparatus are particularly suitable foragglomerating finely divided carbonaceous materials at an elevatedtemperature and forming a substantial quantity of agglomerates having apreselected size range. The carbonaceous materials at an elevatedtemperature are introduced into a rotating drum which serves as a retortand a layer of carbonaceous material is deposited on the retort innercylindrical wall. A plurality of longitudinally extending spaced ridgesand valleys are formed in the layer of carbonaceous material with theridges and valleys extending substantially parallel to the retortlongitudinal axis. After the binder in the carbonaceous particles isevolved the layer of carbonaceous material loses its plasticity andrigidifies to form a relatively rigid layer with ridges and valleysformed therein.

As other finely divided carbonaceous material is introduced into therotating retort the carbonaceous material forms a bed in the retort withan upper surface extending upwardly in the direction of rotation of theretort. The longitudinally extending ridges of carbonaceous materialformed on the inner wall serve as lifters to convey or lift a portion ofthe finely divided carbonaceous material adjacent the retort inner wallin the direction of retort rotation and deposit at least a portion ofthis carbonaceous material on the upper surface of the bed to bothintimately mix the finely divided carbonaceous material in the retortand deposit particles on the upper inclined surface of the bed. Repeatedtumbling of the particles and partially formed agglomerates on the uppersurface of the bed causes continued growth to form agglomerates of apreselected size. Any finely divided carbonaceous material deposited onthe exposed surface of the ridges and valleys is continually removedtherefrom so that the ridges and valleys of a preselected configurationare maintained during the agglomeration process. Where desired, metalliclifters, such as elongated metallic members, of proper dimension may besecured to the retort inner wall to provide support for thelongitudinally extending ridges of carbonaceous material and also serveas an integral portion of the lifters.

With the above arrangement a plurality of spaced elongated ridges isformed on the inner wall of the rotating retort to serve as lifting ormixing devices for the finely divided carbonaceous material. The scraperpositioned in the retort that initially shaped the elongatedlongitudinally extending ridges and valleys in the layer of carbonaceousmaterial further removes other agglomerative carbonaceous material thatmay be deposited on the surface of the ridges and valleys so that thelayer of carbonaceous material retains its ridge and valleyconfiguration during the agglomeration process.

Accordingly, the principal object of this invention is to provide amethod and an apparatus for forming elongated longitudinally extendingridges and valleys in a layer of agglomerative material deposited on theinner wall of a rotary drum.

Another object of this invention is to provide a method and an apparatusfor maintaining a plurality of spaced longitudinally extending liftersformed of agglomerative material on the inner wall of a rotary drum.

These and other objects and advantages of this invention will be morecompletely disclosed and described in the following specification, theaccompanying drawings and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top plan view of a rotary drum assembly having separateballing and hardening drums.

FIG. 2 is a view in side elevation of the rotary drum assembly,illustrating the rotary scraper rotatably supported in the balling drum.

FIG. 3 is an enlarged view of the balling drum in side elevation andsection, illustrating the support and drive for the rotary scraper andschematically the longitudinally extending rows of scraper blades.

FIG. 4 is a view in section taken along the line IV--IV of FIG. 3,illustrating in detail the rotary scraper with four rows of scraperblades extending radially therefrom.

FIG. 5 is a fragmentary view in section taken along the line V--V ofFIG. 4, illustrating a scraper blade element of a row of scraper bladesadjustably secured to the blade support.

FIG. 6 is a view in end elevation of the balling drum feed andillustrating the relative position of the rotary scraper in the ballingdrum.

FIG. 7 is a diagrammatic view in section and in elevation of the ballingdrum, illustrating schematically the rotary scraper within the ballingdrum rotating in the same direction as the direction of the drumrotation and the manner in which the longitudinally extending ridges andvalleys are formed in a layer of agglomerative material on the innerwall of the drum with the longitudinally extending ridges serving aslifters for the particulate agglomerative material within the ballingdrum.

FIGS. 8, 9, 10, 11 and 12 are fragmentary views in section similar toFIG. 7, illustrating the number and types of longitudinally extendingridges and valleys formed in the layer of agglomerative material whenthe rotary scraper is rotated at speeds of 4, 5, 6, 7 and 8 times fasterthan the speed of the drum respectively.

FIG. 13 is a graphical representation of the heights of the ridgesformed in the layer of agglomerative material when the rotary scraper isrotated in the same direction as the rotary drum and at various ratiosof scraper speed to drum speed with a drum having an effective diameterof 141 inches and a scraper having a diameter of 46.1 inches.

FIG. 14 is a schematic longitudinal section of the agglomerating drum,illustrating the configuration of the longitudinally extending ridgesand valleys formed in the layer of agglomerative material deposited onthe inner surface of the agglomerating drum.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Throughout the specification the rotary cylindrical drum will also bereferred to as rotary retort or kiln. The terms rotary retort or kilnare intended to designate a cylindrical drum in which partialdistillation of one or more of the constituents takes place during theagglomeration process. Although the preferred method includes thepartial distillation of coal during the agglomeration process, it shouldbe understood that it is not intended to limit the invention to such aprocess and the invention may be practiced with materials thatagglomerate at ambient temperature. It is not intended, by illustratingand describing the rotary cylindrical drum assembly herein as includinga separate agglomerating drum and a separate hardening drum, to belimited to such an assembly. The invention may also be practiced in asingle cylindrical drum assembly. The agglomerating drum in thisspecification is also referred to as a balling drum.

Referring to the drawings and particularly FIGS. 1 and 2 there isillustrated a rotary drum assembly generally designated by the numeral10 that includes separate balling and hardening drums designated by thenumerals 12 and 14, respectively. The balling drum 12 has a generallycylindrical configuration with a front feed or inlet opening 16 and arear discharge opening 18 and a longitudinal axis 15 about which theballing drum 12 rotates. The discharge opening 18 of drum 12 extendsinto a stationary housing 20. The hardening drum 14 also has a generallycylindrical configuration with an inlet opening 22 that extends into thefixed stationary housing 20 and a discharge opening 24 with a trommelscreen 26 connected thereto. The trommel screen 26 is enclosed by ahousing 28 that has outlets 30 and 32 for agglomerates separatedaccording to size by the trommel screen 26. As shown in FIG. 3, thedischarge opening 18 of balling drum 12 extends into the inlet opening22 of hardening drum 14 so that agglomerates formed in the balling drum12 are discharged directly into the hardening drum 14. The balling drumoutlet opening 18 has an annular dam 34 that controls the inventory ofagglomerative material and agglomerates in the balling drum 12. A sealedhousing 36 surrounds the balling drum inlet opening 16 and, asillustrated in FIG. 6, suitable inlets 38 and 40 are provided in thehousing 36 for introducing agglomerative material, such as coal andchar, into the balling drum 12.

As illustrated in FIGS. 1 and 2, the balling drum 12 has an annular gear42 secured thereto that meshes with a drive gear 44 connected to asuitable drive means designated by the numeral 46. The balling drum 12has a pair of annular metallic tires 48 and 50 that rotatably supportthe drum 12 on roller assemblies 52 and 54 and limit axial movement ofballing drum 12. The roller assemblies 52 and 54 and the front housing36 are supported on a platform 58 that is movable vertically to changethe angle of inclination of the balling drum 12. The balling drumlongitudinal axis 15, i.e. the axis of rotation, is substantiallyhorizontal and where desired the platform 58 may be utilized to inclinethe balling drum 12 axis of rotation to control the residence time ofthe material therein. The hardening drum 14 has a similar annular gear60 secured thereto that meshes with a drive gear 62. A separate drivemeans 64 rotates the hardening drum 14 at a preselected speed that isindependent of the speed of rotation of the balling drum 12. Annularmetallic tires 66 and 68 support the hardening drum 14 on rollerassemblies 70 and 72 to permit rotation of the hardening drum 14 by thedrive means 64 and prevent axial movement of the hardening drum 14during rotation thereof.

Referring to FIGS. 3 and 6, a scraper generally designated by thenumeral 74 has a longitudinal axis 75 and is rotatably positioned withinthe balling drum 12 in spaced relation to the drum inner wall 76. Therotary scraper 74 is located above a horizontal plane extending throughthe longitudinal axis 15 of the drum 12 and, as viewed in FIG. 6, on theleft side of a vertical plane extending through the longitudinal axis ofdrum 12. With this arrangement the rotary scraper 72 is positioned inthe upper left quadrant of the cylindrical opening in the balling drum12 as defined by the inner drum wall 76 and is arranged to rotate aboutits longitudinal axis 75. As later explained, the position of the rotaryscraper is determined by the direction of drum rotation. For example, asviewed in FIGS. 6 and 7, drum rotation is in a counter-clockwisedirection as indicated by the directional arrow 78 and the rotaryscraper 74 is positioned in the upper quadrant opposite from theinclined bed of agglomerative material formed within balling drum 12.

The rotary scraper 74 has a tubular body portion 80 with a front endshaft 82 and a rear end shaft 84 secured thereto and extendingtherefrom. It should be understood that the body portion 80 may also besolid and of a configuration other than a cylinder. The body portion 80may have a smaller transverse dimension than illustrated as long as thebody portion has sufficient strength to rotatably support the blades.The front end shaft 82 extends through a suitable seal 86 in the housing36 and is rotatably supported in a bearing 88 mounted on the housing 36.The front end shaft 82 has a sprocket 90 nonrotatably secured theretoand the front end shaft is supported in another bearing 94 which, inturn, is supported on a fixed beam 92. The rear end shaft 84 isrotatably supported in a bearing 96 which is supported on a fixedsupport beam 98. The beam 98 is secured to a portion of the fixedhousing 20 enclosing the balling drum outlet opening 18 and thehardening drum inlet opening 22. With this arrangement the scraper 74 isrotatably supported within the balling drum 12 and is supported at itsend portions in bearings.

The drive for rotating the scraper 74 includes a drive motor 100,illustrated in FIGS. 3 and 6, connected through a suitable speed reducer102 to a drive sprocket 104. An endless chain 106 is reeved about thesprockets 90 and 104 and is arranged to rotate the scraper 74 in thesame direction as the direction of rotation of the drum 12 as indicatedin FIGS. 3, 6 and 7 by the directional arrow 56. Suitable control meansare provided to rotate the scraper 74 in synchronous relation with theballing drum 12 so that the scraper 74 rotates at a preselected speedratio with the balling drum 12. Where desired the control means can bearranged to change the relative speeds of the scraper or the drum toobtain other speed ratios between the scraper and the drum so that, aslater discussed, other ridge and valley configurations may be obtained.

The scraper 74 has four rows of scraper blades generally designated bythe numerals 108, 110, 112 and 114 secured to the outer surface of thetube 80. The rows of blades include separate blade assemblies that havea blade support member 116 rigidly secured to the surface of the tube 80as by welding or the like. Separate blades or blade segments are securedto the blade support members 116 by means of bolts 120. The bladesegments 118 have elongated slotted portions 122 that permit radialadjustment of blade segments 118 on the blade support members 116.

The rows of blades 108, 110, 112 and 114 are parallel and extendlengthwise along the tube 80 to form elongated continuous cuttingsurfaces along substantially the entire length of the scraper 74. InFIG. 3 only the end portions of the rows of blades 108, 110, and 112 areillustrated. The continuous cutting surface formed by the rows of bladespreferably follows an arcuate generally helical path in which the helixhas less than a single turn about the axis 75 of the tube 80 throughoutthe length of the scraper 74 as is diagrammatically illustrated by the--.sup.. -- line 124 in FIG. 3.

The scraper 74 thus has four separate rows of blades extendinglengthwise throughout substantially the entire length of the scraper 74.The rows of blades follow a helical path and preferably form a helix notexceeding a single turn about the tube axis in which the rows of bladesare displaced to the left about the axis 75 as viewed in FIG. 3 betweenthe front and rear of the scraper 74. It should be understood that otherblade configurations may be employed that have the rows of bladesarranged parallel to the longitudinal axis of the scraper tube 80 orform a helix with more than one turn about the tube axis. The bladearrangement should be such, however, that the ridges formed in thematerial adhering to the drum inner wall extend longitudinally along thedrum inner surface and are substantially parallel to the axis of thedrum. With this arrangement the ridges formed by the blades serve aslongitudinally extending lifters to lift and mix the material in thedrum.

It should also be understood that the number of rows of blades securedto the outer surface of the tube 80 can be increased or decreased as,for example, the scraper 74 can have one, two or three rows of bladesrather than four rows as illustrated. It is desirable, however, that therows of blades be equidistantly positioned on the periphery of thescraper tube 80 to provide symmetrical ridges and valleys in the layerof agglomerative material deposited on the balling drum inner wall 76.

Referring to FIGS. 7 and 14, there is illustrated diagrammatically themanner in which the rotary scraper 74 forms ridges and valleys in thelayer of agglomerative material deposited on the inner wall 76 ofballing drum 12 and the manner in which the ridges serve as lifters toadmix the agglomerative constituents and aid in forming agglomerates ofa preselected size range from the agglomerative material.

To form a corrugated or scalloped surface with longitudinally extendingridges and valleys on the wall of the balling drum, agglomerativematerial is first introduced into the balling drum. Where particulatebituminous coal, finely divided char and pitch are the agglomerativeconstituents, the coal may be preheated to a temperature of between 400°F. and 625° F. which is below the temperature at which the surface ofthe coal particles becomes plastic and sticky. The char is preheated toa temperature between 1000° F. and 1200° F. to supply the sensible heatrequired for the agglomeration process. The coal, char and pitch at theabove elevated temperatures are introduced into the balling drum 12 asthe balling drum 12 is rotating in a counterclockwise direction asillustrated in FIG. 7.

The agglomerative constituents are mixed by the rotation of the drum 12and heat is transferred from the char to the coal particles and pitchand the agglomerative constituents form a sticky plastic mass. A layerof the sticky plastic mass is deposited on the inner surface 76 ofballing drum 12. The rotary scraper 74 is synchronously rotated in thesame direction as the direction of rotation of the balling drum 12 andat 6 times the speed of the balling drum 12. At this synchronous speedthe rows of scraper blades 108, 110, 112 and 114 periodically movetoward and away from the wall of the drum 12.

Because the rotation of the scraper is synchronous with the rotation ofthe drum at a ratio of 6 to 1, 24 elongated ridges generally designatedby the numeral 130 are formed in the layer of agglomerative material126. The rows of scraper blades are so spaced from the drum wall 76 thatthe layer of agglomerative material deposited on the drum wall 76 iscontinuous and elongated valleys generally designated by the numeral 132are formed in the agglomerative material between the ridges 130. Whilethe layer of agglomerative material is being deposited on the drum wall76 and is being shaped by the scraper 74 the agglomerative material inthe layer is plastic and flexible. When the binder associated with thecoal and pitch loses its plasticity due to the pyrolysis that takesplace at the elevated temperature within the drum the layer hardens andrigidifies to retain the longitudinally extending ridge and valleyconfiguration above discussed.

The material to be formed into agglomerates, preferably the samematerial employed in forming the corrugated or scalloped layer on thedrum wall, may be introduced into the drum while the layer is hardeningor after the layer has hardened. The agglomerative material isintroduced on a continuous basis into the rotating drum at a preselectedrate to form a bed of agglomerative material within the drum. The bed isdesignated by the numeral 134 in FIG. 7. Rotation of the drum in thedirection indicated by the arrow 78 moves the bed of agglomerativematerial upwardly along one side of the retort to an extent that the topsurface 136 of bed 134 has, for example, an angle of repose of about70°. The angle of repose is dependent on the speed of rotation of thedrum 12. As the drum 12 rotates the longitudinally extending ridges 130in the layer 126 move under the bed of agglomerative material andpromote agitation of the bed. The agitation of the bed includes top tobottom mixing whereby a portion of the agglomerative material in the bedadjacent the drum wall 76 is conveyed upwardly through the bed. Thelongitudinally extending ridges further turn a substantial portion ofthis agglomerative material in the portion conveyed by thelongitudinally extending ridges and valleys over and onto the bed topsurface 136.

Moving a portion of the agglomerative material upwardly through the bedand turning a portion of the agglomerative material over thoroughlyadmixes the agglomerative material and also continuously depositspartially agglomerated agglomerates 138 on the bed upper surface 136.The partially agglomerated agglomerates 138 roll down the bed uppersurface 136 and the partially agglomerated agglomerates grow in size bypicking up additional plastic particles from the upper surface of thebed. In order to obtain the above described bottom mixing of theagglomerative material it is essential that the ridges 130 extendlongitudinally along the inner surface of the drum, as illustratedschematically in FIG. 14, to be effective as lifters. The angle ofinclination of balling drum 12 conveys the partially agglomeratedagglomerates as they grow toward the balling drum discharge opening 18.The partially agglomerated agglomerates continue to grow until thebinder loses its plasticity and full size agglomerates then harden andrigidify. After the agglomerates harden no further growth takes place.The agglomerates so formed are introduced into the hardening drum whererotation of the hardening drum permits substantial completion of thepyrolysis of the agglomerative constituents and relatively rigid hardagglomerates are withdrawn from the hardening drum.

The agglomerative material in bed 134 because of its plasticity has atendency to adhere to the interior surface of the layer of rigidagglomerative material deposited on the drum inner wall 76. The scraperassembly 74, because of its continued rotation at a preselectedsynchronous speed, continuously removes the fresh deposit ofagglomerative material on the outer surface of the ridges and valleyswhile the newly deposited agglomerative material is in a relativelyplastic state to thereby maintain the configuration of ridges andvalleys as illustrated in FIG. 7. Where desired metallic support membersmay be secured to the drum inner wall and the ridge portions 130 formedthereon. The metallic support members provide structural support for theridges and the synchronous rotation of the scraper 74 preventsinterference between the metallic support members and the scraperblades.

It may be desirable for certain agglomerative conditions to vary thenumber and height of the longitudinally extending ridges and valleysformed around the periphery of the drum wall to increase the previouslydescribed mixing of the agglomerative material. FIGS. 8, 9, 10, 11 and12 illustrate the versatility of the method and apparatus for producinglongitudinally extending ridges of a desired height and differentnumbers of longitudinally extending ridges and valleys in the layer ofmaterial on the drum wall.

FIG. 8 illustrates the ridge and valley configuration formed when therotary scraper 74 is rotating in the same direction as the balling drum12 as indicated by the arrows 78 and 56 with the rotary scraper 74rotating 4 times faster than the balling drum 12. The ridges 130 have aflat arcuate upper surface 140 that is formed by the scraper tube 80rubbing on the upper surface of the ridges 130 to thus limit the heightof ridges 130. It should be understood, however, that the tube 80 mayhave a reduced diameter to provide a greater effective length for thescraper blades 108, 110, 112 and 114. Without interference from thescraper tube 80 the height of the ridges 130 could be increasedsubstantially. The valleys 132 are relatively narrow valleys in FIG. 8where the rotary scraper 74 is rotating at a speed 4 times faster thanthe speed of the drum 12.

In FIG. 9 the rotary scraper 74 is rotating at a speed 5 times fasterthan the balling drum 12 and 20 longitudinally extending ridges 130 areformed in the layer of agglomerative material 126. The valleys 132 arebroader than the valleys 132 illustrated in FIG. 8 and the ridges 130have a flat arcuate upper surface 140 caused by the scraper tube 80rubbing against the ridge upper surface. Thus, the scraper tube 80 alsolimits the height of the ridge in FIG. 9 and the effective height of theridges could be increased substantially by reducing the diameter of thescraper tube 80.

In FIG. 10 there is schematically illustrated the ridge and valleyconfiguration that is obtained when the rotary scraper 74 rotates 6times faster than the balling drum 12. This ridge and valleyconfiguration is also illustrated in FIG. 7. With this arrangement 24ridges 130 and twenty-four valleys 132 are formed around the peripheryof the drum 12. The height of the ridges 130 is less than the ridgesillustrated in FIG. 9 and the scraper tube 80 does not interfere withthe ridge formation so that the ridges have a pointed upper portion 142.The width of the valleys in FIG. 10 is increased when compared with thevalleys illustrated in FIGS. 8 and 9.

FIG. 11 diagrammatically illustrates the ridge and valley configurationformed in the layer of agglomerative material when the rotary scraper 74is rotating at a speed 7 times faster than the speed of the drum 12 andin the same direction as the drum 12. At this speed ratio of 7 to 1 28ridges and 28 valleys are formed about the periphery of the drum. Theridges have a reduced height when compared with the ridges formed by thescraper at a lower speed ratio as, for example, 6 to 1 as illustrated inFIG. 10.

FIG. 12 illustrates the ridge and valley configuration formed when thespeed ratio between the scraper and the drum is 8 to 1. At this speedratio 32 ridges and 32 valleys are formed in the agglomerative materialaround the periphery of the balling drum 12. The ridge height in FIG. 12is further reduced from the ridge height illustrated in FIGS. 10 and 11.It will thus be apparent where a greater number of ridges and valleysare desired the ridge height is reduced as the number of ridges andvalleys are increased.

With the above described method, it is essential that the product of thenumber of rows of blades on the scraper multiplied by the ratio ofscraper revolutions to drum revolutions per unit time is a whole number.##EQU2## wherein N = number of ridges formed

b = number of scraper blades

U₁ = drum speed, rpm

U₂ = scraper speed, rpm.

For example, with a scraper having four rows of blades and the scraperrotating 7 times faster than the drum, 28 longitudinally extendingridges and valleys are formed and the rows of blades will sequentiallymove in timed relation through the longitudinally spaced valleys withoutdisturbing the adjacent ridges.

Where 22 ridges are desired and the rotary scraper has four rows ofblades, the ratio of scraper speed to drum speed must be 5.5, asexemplified by the following calculation.

N = 4 × 5.5

n = 22

fig. 13 illustrates diagrammatically the manner in which the ridgeheight increases with the decrease in the ratio of scraper speed to drumspeed. It will be apparent from FIGS. 8 - 12 and the graph that variousconfigurations of ridge height and numbers of ridges can be formed inthe layer of agglomerative material when the rotary scraper 74 isrotated in the same direction as the balling drum. It should be notedthat it is also possible with the above method and apparatus to controlthe thickness of the layer and form ridges and valleys in the layer sodeposited on the drum inner wall. The blades on the scraper as theyrotate relative to the drum follow arcuate overlapping paths through thelayer and thus form the ridges and valleys above discussed.

With the above method and apparatus it is now possible to form liftersof varying number and configuration on the inner surface of the drumfrom the same or substantially the same material that is agglomerated inthe drum. After the lifters in the form of longitudinally extendingridges are formed in the layer of material deposited on the wall of thedrum the blades of the rotary scraper 74 remove the material that isdeposited on the surface of the ridges and valleys in the layer duringthe agglomeration process.

According to the provisions of the patent statutes, we have explainedthe principle, preferred construction and mode of operation of ourinvention and have illustrated and described what we now consider torepresent its best embodiments. However, it should be understood that,within the scope of the appended claims, the invention may be practicedotherwise than as specifically illustrated and described.

We claim:
 1. A method for agglomerating finely divided agglomerativematerial comprising,feeding finely divided agglomerative material into asubstantially horizontal rotating drum having an inner wall, said drumhaving a longitudinal axis and said drum arranged to rotate about saidlongitudinal axis, depositing a layer of said finely dividedagglomerative material on said drum inner wall, rotating alongitudinally extending scraper in said drum in the same direction ofrotation as said drum in fixed timed relation to the rotation of saiddrum to form a preselected number of longitudinally extending ridgesaccording to the following formula: ##EQU3## N = a whole number andnumber of ridges formed b = number of scraper bladesU₁ = drum speed, rpmU₂ = scraper speed, rpm, forming a plurality of elongated alternatingand longitudinally extending ridges and valleys in said layer, saidridges and valleys extending substantially lengthwise along said druminner wall and substantially parallel to said drum longitudinal axis,controlling the ratio of speeds of said rotating drum and said rotatingscraper to control the height and number of longitudinally extendingridges and valleys formed in said layer, and maintaining said sameridges and same valleys so formed in said layer deposited on the druminner wall while rotating said drum and forming agglomerates from otherfinely divided agglomerative material introduced into said rotary drum.2. A method for agglomerating finely divided agglomerative material asset forth in claim 1 which includes,forming a bed of other finelydivided material in said drum, rotating said drum and forming an upperinclined surface on said bed, moving said longitudinally extendingridges and valleys under said bed and lifting a portion of said otheragglomerative material adjacent said drum inner wall with saidlongitudinally extending ridges and valleys and thereafter depositingthe lifted portion of said other agglomerative material on the upperinclined surface of said bed.
 3. A method for agglomerating finelydivided agglomerative material as set forth in claim 1 whichincludes,rotating said scraper at a speed 6 times the speed of therotating drum to thereby form 24 longitudinally extending ridges and 24longitudinally extending valleys in said layer.
 4. A method foragglomerating finely divided agglomerative material as set forth inclaim 1 which includes,rotating said scraper at a speed 8 times thespeed of the rotating drum to thereby form 32 longitudinally extendingridges and 32 longitudinally extending valleys in said layer.
 5. Amethod for agglomerating finely divided agglomerative material as setforth in claim 1 in which,said finely divided agglomerative materialincludes bituminous coal and char heated to an elevated temperaturebefore being introduced into said rotating drum.